import {ajax} from 'rxjs/ajax';
import {forkJoin} from 'rxjs';
// forkJoin 当所有的Observable 完成时，发射最后的值。
{
     const result$ = forkJoin(  
        {
          google: ajax.getJSON('https://api.github.com/users/google'),
          microsoft: ajax.getJSON('https://api.github.com/users/microsoft'),
          users: ajax.getJSON('https://api.github.com/users')
        }
      )
      result$.subscribe(val => console.log(val))
       // { google: object, microsoft: object, users: array }
}